Cardiovascular effects of i.c.v. administration of serotonin and
the 5-ht1a agonist dp-5-ct in conscious long-evans and brattleboro
rats.
Andrew, Ian K. Anderson, G. Ramage & Sheila M. Gardiner.
Department of Physiology and Pharmacology, University of Nottingham
Medical School, Queen's Medical Centre, Nottingham NG7 2UH and the
Academic Department of Pharmacology Royal Free Hospital School of
Medicine, Rowland Hill St, Hampstead, London NW3 2PF. U.K.
APStracts 3:0141R, 1996.
The regional hemodynamic changes caused by i.c.v. 5-HT were
investigated in conscious Long-Evans and Brattleboro rats with
chronically implanted Doppler flow probes. In both strains a low dose
of 5-HT ( 4 nmol kg-1) caused a pressor response associated with
tachycardia, mesenteric vasoconstriction and a transient hindquarters
vasodilatation. In Long Evans rats, higher doses of 5-HT (40 & 120
nmol kg-1) caused a pressor response, a bradycardia, mesenteric
vasoconstriction and maintained hindquarters dilatation. The
bradycardia and mesenteric vasoconstriction caused by 40 nmol kg-1 of
5-HT in Long-Evans rats were attenuated by d(CH2)5Tyr(Me)AVP a V1
-receptor antagonist. In Brattleboro rats the high doses of 5-HT
failed to cause a pressor response but caused a delayed depressor
response, a transient tachycardia, less mesenteric vasoconstriction
and a larger initial hindquarters dilatation compared with Long-Evans
rats. The initial part of the hindquarters vasodilator response
caused by 120 nmol kg-1 of 5-HT in Brattleboro rats was attenuated by
the [beta]2-adrenoceptor antagonist, ICI 118551. In Long-Evans rats,
DP-5-CT (3, 30 & 100 nmol kg-1; i.c.v), a 5-HT1A receptor agonist,
caused a tachycardia associated with a marked hindquarters
vasodilatation. These changes were accompanied by a weak mesenteric
vasoconstriction and, for the highest dose of DP-5-CT, a pressor
response. These data overall are consistent with the hemodynamic
effects of i.c.v. 5-HT contingent upon vasopressin release and, along
with DP-5-CT, sympathoadrenal excitation; however additional
mechanisms are indicated.
Received 14 March 1995; accepted in final form 26 February 1996.
APS Manuscript Number R166-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 23 April 96